In 2020, Miami sank 73 concrete sections from the SW 1st Street Bridge to create an artificial reef; the pieces now provide habitat 8 feet above the seabed

On February 19th, 2020, divers in Miami watched 73 sections of an old demolished bridge being sunk into the Atlantic Ocean to form an artificial reef. Instead of transporting the slab sections that used to support the SW 1st Street Bridge across the Miami River to landfill, the Miami-Dade County government sank the slabs into the Julia Tuttle Artificial Reef Site. This means that the slabs are now approximately 8ft above the seabed and are slowly becoming a new home for fish, sponges, and coral larvae.

This is one of many projects carried out by the county’s Artificial Reef Program. Since 1981, the program has sunk military tanks, old boats, and oil rigs, among other materials. It’s a story that appeals to anyone drawn to the idea of reducing, reusing, and recycling, raising the question of whether it truly helps the ocean.

What happens to a demolished bridge?


When a bridge is replaced, it isn’t exactly recycled. The SW 1st Street Bridge had to be demolished as part of a Florida Department of Transportation project, and instead of being crushed and taken to landfill, the 736 tonnes of concrete piles were transported on barges and sunk into place. This has almost created a new piece of infrastructure, as the bridge is providing shelter to snapper, grouper and invertebrates.

Science says concrete is the best

All around the world, people have been creating artificial reefs from junk, and scientists have tried to see if it actually works. A 2021 paper titled “Marine artificial reefs, a meta-analysis of their design, objectives and effectiveness,” published in the journal Global Ecology and Conservation, by Baptiste Vivier et al., looked at 127 scientific studies around artificial reefs worldwide and showed concrete always performed the best. This is due to its textured surface.

The good news is that concrete performed well in the analysis. The downside is that artificial reefs still fall short of natural ones overall. A separate 2024 analysis titled “A global meta-analysis of ecological effects from offshore marine artificial structures,” by Anaëlle Lemasson’s team and published in the journal Nature Sustainability, looked at 531 data points from over 100 studies. They looked at how artificial structures compared to natural reefs and sandy seabeds. The findings were mixed: artificial reefs supported more fish than bare sand or mud, but hosted significantly fewer invertebrates than natural coral reefs, meaning artificial reefs are an improvement over barren seabed, but no substitute for a natural reef. No serious study claims otherwise.

Why this matters

This isn’t just a quirky local news story. The US has thousands of miles of old bridges, piers and seawalls that will need replacing in the future. Most demolition waste in the country is sent to landfill. This is one of the very few examples where ‘circular economy’ is a real part of the county’s budget. As this generation has become very sceptical towards greenwashing by companies, this is a great example, as it is much cheaper than transporting the concrete to a landfill site, and it helps marine life.

While it won’t help Florida’s struggling reefs (which are struggling due to warming waters and diseases), it is a small win to show we aren’t seeing demolition as waste. This can be easily replicated in other coastal cities that have old bridges. Just be realistic with what it can do.